kernel TechnoTwirl
<
	// filter: "TechnoDots";
	// nameSpace: "popforge::ImageProcessing";
	// vendor: "joa ebert";
	// version: 1;
	// description: "like a pixelate filter but using nice dots with spacing";
	
	// filter: "Twirl";
	// nameSpace: "popforge::ImageProcessing";
	// vendor: "joa ebert";
	// version: 1;
	// description: "applies twirl displacement map";
	
	mashup: "TechnoTwirl";
	nameSpace: "ebod@";
	vendor: "mangler";
	version: 1;
	description: "mashup of the Twirl and TechnoDot filters written by joa ebert";
>
{
	parameter float spacing
	<
		minValue:     float(0.0);
		maxValue:     float(16.0);
		defaultValue: float(2.0);
	>;
	
	parameter float radius
	<
		minValue:     float(1.0);
		maxValue:     float(64.0);
		defaultValue: float(4.0);
	>;
	
	parameter float angle
	<
		minValue:     -20.000;
		maxValue:      20.000;
		defaultValue:   0.000;
	>;
	
	parameter pixel4 fillColor
	<
		minValue:     pixel4(0.0, 0.0, 0.0, 0.0);
		maxValue:     pixel4(1.0, 1.0, 1.0, 1.0);
		defaultValue: pixel4(0.0, 0.0, 0.0, 1.0);
	>;
	
	void evaluatePixel(in image4 source, out pixel4 sink)
	{
		float2 xy0 = outCoord();
		float2 xy1 = xy0;
		
		// aabb of dot with spacing
		float rs = radius * 2.0 + spacing;
		
		// shift into square
		xy1 -= mod( xy1, float2(rs, rs) );
		
		// put into the middle
		xy1 += float2(radius);
		
		if (length(xy0 - xy1) > radius) sink = fillColor;
		else
		{
			float2 center = xy1;
			float2 delta  = xy0 - center;
			
			float d = length(delta);
			float r = radius;
			float phi = atan(delta.y, delta.x) + angle * (r - d) / r;
			
			xy1 = center + float2(d * cos(phi), d * sin(phi));
			
			pixel4 c0 = sampleLinear(source, xy0);
			pixel4 c1 = sampleLinear(source, xy1);
			
			sink = (d < r)? c1: c0;
		}
	}
}